Liquid crystal display devices are currently used in a variety of applications. In a general liquid crystal display device, one color display pixel is comprised of three pixels respectively representing red, green and blue, which are the three primary colors of light, thereby conducting a display operation in colors.
A known liquid crystal display device, however, can reproduce colors that fall within only a narrow range (which is usually called a “color reproduction range”), which is a problem. If the color reproduction range is narrow, then some of the object colors (i.e., the colors of various objects existing in Nature, see Non-Patent Document No. 1) cannot be represented. Thus, to broaden the color reproduction range of liquid crystal display devices, a technique for increasing the number of primary colors for use to perform a display operation has recently been proposed.
For example, Patent Document No. 1 discloses a liquid crystal display device 800 in which one color display pixel P is made up of four pixels that include not only red, green and blue pixels R, G and B representing the colors red, green and blue, respectively, but also a yellow pixel Y representing the color yellow as shown in FIG. 12. That liquid crystal display device 800 performs a display operation in colors by mixing together the four primary colors red, green, blue and yellow that are represented by those four pixels.
By increasing the number of primary colors for use to conduct a display operation (i.e., by performing a display operation using four or more primary colors), the color reproduction range can be broadened compared to a known liquid crystal display device that uses only the three primary colors for display purposes. Such a liquid crystal display device that conducts a display operation using four or more primary colors will be referred to herein as a “multi-primary-color liquid crystal display device”.
However, if the number of primary colors for use to conduct a display operation is increased, then the number of pixels per color display pixel increases, and therefore, the area given to each of those pixels should decrease if the area of one color display pixel remained the same. Consequently, the lightness of the color represented by each pixel should decrease. For example, if the number of primary colors for use to conduct a display operation is increased from three to four, the area given to each pixel decreases to three-quarters, and the lightness of each pixel drops to three-quarters, too. Also, if the number of primary colors for use to conduct a display operation is increased from three to six, the area given to each pixel decreases to one half, and the lightness of each pixel drops to one half, too.
As for a pixel representing the color green or yellow, even if its lightness decreases to a certain degree, the pixel can still represent various object colors well enough. As for a pixel representing the color red, however, if its lightness decreases, the display quality of some of those object colors declines. In this manner, if the lightness decreases due to an increase in the number of primary colors to use, the display quality of the color red will be debased and the color red will turn into a blackish red (i.e., a dark red).
A technique for overcoming such a problem is proposed in Patent Document No. 2. FIG. 13 illustrates a liquid crystal display device 900 as disclosed in Patent Document No. 2. Each color display pixel P of the liquid crystal display device 900 is made up of red, green, blue, and yellow pixels R, G, B and Y. In the liquid crystal display device 900, however, the red and blue pixels R and B have the larger area and the green and yellow pixels G and Y have the smaller area. By setting the area of the red pixel R to be larger than in a situation where a single color display pixel P is simply equally divided into four, the lightness of the color red increases, and therefore, a bright red can be represented.